Scientists at the European XFEL and DESY produce high-power attosecond X-ray pulses at megahertz repetition rates

Highly accelerated electrons (blue cloud) are strongly compressed with the help of special beam optics (bright line in the centre). This leads to very bright X-ray pulses (yellow) with pulse durations of only a few hundred attoseconds and powers in the terawatt range. @ European XFEL, Tobias Wüstefeld

A research team at European XFEL and DESY has achieved a major advance in X-ray science by generating unprecedented high-power attosecond hard X-ray pulses at megahertz repetition rates. This advancement opens new frontiers in the study of ultrafast electron dynamics and enables non-destructive measurements at the atomic level. The researchers published their results now in Nature Photonics. Researchers have demonstrated single-spike hard X-ray pulses with pulse energies exceeding 100 microjoules and pulse durations of only a few hundred attoseconds. An attosecond is one quintillionth () of a second—a timescale that allows scientists to capture even the fastest electron movements in matter.

“These high-power attosecond X-ray pulses could open new avenues for studying matter at the atomic scale,” says Jiawei Yan, physicist at European XFEL and lead author of the study published in Nature Photonics. “With these unique X-rays, we can perform truly damage-free measurements of structural and electronic properties. This paves the way for advanced studies like attosecond crystallography, allowing us to observe electronic dynamics in real space.”

Traditional methods for generating such ultra-short hard X-ray pulses required dramatically reducing the electron bunch charge to tens of picocoulombs, which limited the pulse energy and practical use. The team developed a self-chirping method, utilizing the collective effects of electron beams and specialized beam transport systems at the European XFEL. This approach enables the generation of attosecond X-ray pulses at terawatt-scale peak power and megahertz repetition rates without reducing the electron bunch charge.

“By combining ultra-short pulses with megahertz repetition rates, we can now collect data much faster and observe processes that were previously hidden from view,“ says Gianluca Geloni, group leader of the FEL physics group at the European XFEL. “This development promises to transform research across multiple scientific fields, especially for atomic-scale imaging of protein molecules and materials and investigating nonlinear X-ray phenomena.” Reference

Terawatt-attosecond hard X-ray free-electron laser at high repetition rate

Jiawei Yan, Weilun Qin, Ye Chen, Winfried Decking, Philipp Dijkstal, Marc Guetg, Ichiro Inoue, Naresh Kujala, Shan Liu, Tianyun Long, Najmeh Mirian & Gianluca Geloni https://www.nature.com/articles/s41566-024-01566-0 Deutsches Elektronen-Synchrotron DESY